System and method providing resilient data transmission via spectral fragments

ABSTRACT

Systems, methods and apparatus for improving resiliency to interference as well as improved bandwidth utilization in data transmission systems by using spectral fragments to convey respective portions of a data stream or file to be transmitted and independently adapting spectral fragment channel forward error correction (FEC) rate or other parameters in response to interference/impairment conditions.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 13/040,458, filed Mar. 4, 2011, entitled “VIRTUAL AGGREGATIONOF FRAGMENTED WIRELESS SPECTRUM” (Attorney Docket No. 809125), whichapplication is incorporated herein by reference in its entirety.

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/476,571, filed Apr. 18, 2011, entitledINTERFERENCE MITIGATION VIA SLICING AND AGGREGATION OF WIRELESS SIGNALS(Attorney Docket No. 809615); Ser. No. 61/486,597, filed May 16, 2011,entitled EFFICIENT FAILOVER SUPPORT USING AGGREGATION OF WIRELESSSIGNALS (Attorney Docket No. 809663); and Ser. No. 61/523,678, filedAug. 15, 2011, entitled DISJOINT REPLICATED SPREAD SPECTRUM (AttorneyDocket No. 810305) which applications are incorporated herein byreference in their entireties.

TECHNICAL FIELD

The invention relates generally to communication networks and, morespecifically, but not exclusively, to point-to-point andpoint-to-multipoint communication networks and backhaul links.

BACKGROUND

Traditional wireless systems assume the availability of a contiguousblock of spectrum with bandwidth proportional to the amount of data tobe transmitted. Transmission systems are thus frequently designed forworst-case bandwidth requirements with the typical or average use-case,in some instances, requiring much less bandwidth (i.e., spectrum).

Within the context of satellite communications systems and otherpoint-to-point communications systems, available spectrum allocated tocustomers may become fragmented over time, which leads to unused blocksbetween allocated blocks of spectrum. When the blocks of unused spectrumare too small, it is necessary to reallocate spectrum among customers or“move” a customer from existing spectral allocation to a new spectralallocation so that the unused blocks of spectrum may be coalesced into asingle spectral region. Unfortunately, such reallocation is verydisruptive.

SUMMARY

Various deficiencies of the prior art are addressed by the presentinvention of systems, methods and apparatus for improving resiliency tointerference as well as improved bandwidth utilization in datatransmission systems by using spectral fragments to convey respectiveportions of a data stream or file to be transmitted and independentlyadapting spectral fragment channel forward error correction (FEC) rateor other parameters in response to interference/impairment conditions.Various embodiments also provide failover mechanisms adapted to supportto support one or more portions of a protected signal.

A method according to one embodiment comprises dividing a data streaminto a plurality of sub-streams; modulating each sub-stream to provide arespective modulated signal adapted for transmission via a respectivespectral fragment; monitoring data indicative of channel performance foreach of the spectral fragments to identify degraded channels; andadapting, for each degraded channel, one or more respective modulationparameters to compensate for respective identified channel degradation.

BRIEF DESCRIPTION OF THE DRAWINGS

The teachings of the present invention can be readily understood byconsidering the following detailed description in conjunction with theaccompanying drawings, in which:

FIG. 1 depicts a block diagram of a communication system according toone embodiment;

FIG. 2 depicts a graphical representation of a spectral allocationuseful in understanding the present embodiments;

FIG. 3 depicts a high-level block diagram of a general purpose computingdevice suitable for use in various embodiments;

FIGS. 4-6 depicts flow diagrams of methods according to variousembodiments;

FIGS. 7-9 depicts block diagrams of communication systems according tovarious embodiments;

FIG. 10 depicts a high-level block diagram of a slicer/de-multiplexersuitable for use in various embodiments;

FIG. 11 depicts a flow diagram of a method according to one embodiment;

FIG. 12 depicts a high level block diagram of a system benefiting fromvarious embodiments; and

FIG. 13 depicts a flow diagram of a method according to an embodiment.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures.

DETAILED DESCRIPTION

The invention will be primarily described within the context of asatellite communications system. However, those skilled in the art andinformed by the teachings herein will realize that the invention is alsoapplicable to any system benefiting from flexible spectral allocation,such as microwave communications systems, wireless communicationssystems and the like.

One embodiment provides an efficient and general-purpose technique foraggregating multiple, fragmented blocks of wireless spectrum into onecontiguous virtual block such that the cumulative bandwidth is almostequal to the sum of the bandwidths of the constituent blocks. Thefragmented blocks are optionally separated from each other by blocks ofspectrum, such as guard blocks, blocks owned by other parties, blocksprohibited by the wireless spectrum regulatory authority of a region orcountry and so on.

FIG. 1 depicts a block diagram of a communication system benefiting fromvarious embodiments. The communication system 100 of FIG. 1 comprises apoint-to-point link including a virtual spectrum aggregator transmitter110, a power amplifier 120, a satellite uplink 130, a satellite 140, asatellite downlink 150, a virtual spectrum aggregator receiver 160 and,optionally, a control module 170. Data to be transmitted over thepoint-to-point link is provided as a stream of data packets D, such as188-byte transport stream (TS) packets, 64-1500 bytes Ethernet packetsand so on. The specific packet structure, data conveyed within a packetstructure and so on is readily adapted to the various embodimentsdescribed herein.

The input data stream D is received by the virtual spectrum aggregatedtransmitter 110, where it is processed by a slicer/demultiplexer 111 toprovide N sub-streams (D₀ . . . D_(N-1)), where N corresponds to anumber of spectral fragments denoted as S₀, S₁ and so on up to S_(N-1).

As depicted in FIG. 1, N=3 such that the slicer/demultiplexer 111slices, the multiplexes and/or divides the input data stream D into(illustratively) three sub-streams denoted as D₀, D₁ and D₂.

Each of the sub-streams D₀, D₁ and D₂ is coupled to a respectivemodulator 112 (i.e., modulators 112 ₀, 112 ₁ and 112 ₂). Each of themodulators 112 ₀, 112 ₁ and 112 ₂ modulates its respective sub-streamD₀, D₁ and D₂ to provide corresponding modulated signals to be carriedby respective spectral fragments S₀, S₁ and S₂.

The modulators 112 may comprise modulators having the samecharacteristics or having different characteristics, such as thecharacteristics of waveform type, constellation maps, forward errorcorrection (FEC) settings and so on. Each modulator may be optimizedaccording to a specific type of traffic (e.g., streaming media,non-streaming data and the like), the specific channel conditionsassociated with its corresponding spectral fragment S_(i) and/or othercriteria.

Generally speaking, the amount of data allocated by theslicer/demultiplexer 111 to any sub-stream D_(i) is proportional to thedata carrying capacity of the corresponding spectral fragment S_(i). Invarious embodiments, each of the sub-streams D_(i) comprises the sameamount of data, while in other embodiments the various sub-streams D_(i)may comprise different amounts of data.

As depicted in FIG. 1, the first modulator 112 ₀ provides a 6 MHz signalassociated with a first spectral fragment S₀; the second modulator 112 ₁provides a 1 MHz signal associated with a second spectral fragment S₁;and third modulator 112 ₂ provides a 1 MHz signal associated with athird spectral fragment S₂.

A frequency multiplexer (i.e., signal combiner) 113 operates to combinethe modulated signals to produce a combined modulated signal S_(C),which is modulated onto a carrier signal by up-converter 114 to providea modulated carrier signal C. It is noted that multiple frequencymultiplexers/signal combiners 113 may be used to multiplex respectivegroups of modulated signals to be transported via common transponders,microwave links, wireless channels and the like.

In the embodiment of FIG. 1, the spectrum associated with the modulatedcarrier signal C is logically or virtually divided into the plurality ofspectral fragments used to convey the modulated data sub-streams. Thespectral fragment allocation table or other data structure is used tokeep track of which spectral fragments have been defined, which spectralfragments are in use (and by which data sub-streams), and which spectralfragments are available. Generally speaking, eachtransponder/transmission channel may be divided into a plurality ofspectral fragments or regions. Each of these spectral fragments orregions may be assigned to a particular data sub-stream. Each of thedata sub-streams may be modulated according to a unique or commonmodulation technique.

As depicted in FIG. 1, a single satellite transponder is used and,therefore, all of the modulated signals may be combined by frequencymultiplexer 113 prior to up-conversion and transmission via a singlesatellite channel. In various embodiments, multiple transponders withinone or more satellites may be used. In these embodiments, only thosemodulated signals to be transmitted via a common transponder within asatellite are combined and then converted together. In variousembodiments, modulate waveforms are transmitted independently.

The modulated carrier signal C produced by up-converter 114 is amplifiedby power amplifier 120 and transmitted to satellite 140 via satelliteuplink 130. Satellite 140 transmits a modulated carrier signal includingthe modulated sub-streams D₀, D₁ and D₂ to satellite downlink 150, whichpropagates the signal to the virtual spectrum aggregator receiver 160.

Virtual spectrum aggregator receiver 160 includes a downconverter (165)which downconverts a combined spectral fragment signal S_(C)′ from areceived carrier signal C′, and a frequency demultiplexer (164) whichoperates to separate the spectral fragments S₀′, S₁′ and S₂′ from thecombined spectral fragment signal S_(c)′.

Each of the spectral fragments S₀′, S₁′ and S₂′ is coupled to a separatedemodulator (i.e., demodulators 162 ₀, 162 ₁ and 162 ₂). Each of thedemodulators 162 ₀, 162 ₁ and 162 ₂ demodulates its respective spectralfragments S₀′, S₁′ and S₂′ to provide corresponding demodulatedsub-streams D₀′, D₁′ and D₂′.

The demodulated sub-streams D₀′, D₁′ and D₂′ are processed by a combiner161 to produce an output data stream D′ representative of the input datastream D initially processed by the virtual spectrum aggregatortransmitter 110. It is noted that each of the demodulators 162 operatesin a manner compatible with its corresponding modulator 112.

Optionally, virtual spectrum aggregator receiver 160 includes buffers166 ₀, 166 ₁ and 166 ₂ which provide an elastic buffering function forthe various demodulated sub-streams such that alignment errors inducedby different propagation delays associated with the various sub-streamsmay be avoided prior to combining the sub-streams. The buffers in 166are depicted as functional elements disposed between the demodulators(162) and combiner 161. In various embodiments, the buffers 166 or theirfunctional equivalent are included within the combiner 161. For example,combiner 161 may include a single buffer which receives data from all ofthe demodulators (162) and subsequently rearranges that data as outputstream D′. Packet ID and/or other information within the sub-streams maybe used for this purpose.

Optional control module 170 interacts with an element management system(EMS), a network management system (NMS) and/or other management orcontrol system suitable for use in managing network elementsimplementing the functions described herein with respect to FIG. 1. Thecontrol module 170 may be used to configure various modulators,demodulators and/or other circuitry within the elements described hereinwith respect FIG. 1. Moreover, the control module 170 may be remotelylocated with respect to the elements controlled thereby, locatedproximate transmission circuitry, located proximate receiver circuitryand so on. The control module 170 may be implemented as a generalpurpose computer programmed to perform specific control functions suchas described herein. In one embodiment, control module 170 adapts theconfiguration and/or operation of the virtual spectrum aggregatortransmitter 110 and the virtual spectrum aggregator receiver 160 via,respectively, a first control signal TXCONF and a second control signalRXCONF. In this embodiment, multiple control signals may be provided inthe case of multiple transmitters and receivers.

FIG. 2 depicts a graphical representation of a spectral allocationuseful in understanding the present embodiments. Specifically, FIG. 2graphically depicts a 36 MHz spectral allocation in which a firstcustomer is allocated a first portion 210 of the spectrum,illustratively a single 10 MHz block; a second customer is allocated asecond portion 220 of the spectrum, illustratively single 8 MHz block; athird customer is allocated a third portion 230 of the spectrum,illustratively single 10 MHz block; and a fourth customer is allocatedis allocated a fourth portion 240 of the spectrum, illustratively threenoncontiguous spectrum blocks comprising a first 1 MHz block 240 ₁, asecond 1 MHz block 240 ₁ and a 6 MHz block 240 ₃.

Within the context of the various embodiments discussed herein, the datastream associated with the fourth customer is divided into two different1 MHz spectral fragments in a single 6 MHz spectral fragment, each ofwhich is processed in substantially the same manner as described abovewith respect to FIG. 1.

FIG. 3 depicts a high-level block diagram of a general purpose computingdevice 300 suitable for use in various embodiments described herein. Forexample, the computing device 300 depicted in FIG. 3 may be used toexecute programs suitable for implementing various transmitterprocessing functions, receiver processing functions and/or managementprocessing functions as will be described herein.

As depicted in FIG. 3, the computing device 300 includes input/output(I/O) circuitry 310, a processor 320 and memory 330. The processor 320is coupled to each of the I/O circuitry 310 and memory 330.

The memory 330 is depicted as including buffers 332, transmitter (TX)programs 334, receiver (RX) programs 336 and or management programs 338.The specific programs stored in memory 330 depend upon the functionimplemented using the computing device 300.

In one embodiment, the slicer/demultiplexer 111 described above withrespect to FIG. 1 is implemented using a computing device such as thecomputing device 300 of FIG. 3. Specifically, the processor 320 executesthe various functions described above with respect to theslicer/demultiplexer 111. In this embodiment the I/O circuits 310receive the input data stream D from a data source (not shown) andprovide the N sub-streams (D₀ . . . D_(N-1)) to the demodulators 112.

In one embodiment, the combiner 161 described above with respect to FIG.1 is implemented using a computing device such as the computing device300 of FIG. 3. Specifically, the processor 320 executes the variousfunctions described above with respect to the combiner 161. In thisembodiment the I/O circuits 310 receive the demodulated sub-streams D₀′,D₁′ and D₂′ from the demodulators 162 (optionally via buffers 166) andprovide the output data stream D′ representative of the input datastream D initially processed by the virtual spectrum aggregatortransmitter 110.

In one embodiment, the optional control module 170 described above withrespect to FIG. 1 is implemented using a computing device such as thecomputing device 300 of FIG. 3.

Although primarily depicted and described as having specific types andarrangements of components, it will be appreciated that any othersuitable types and/or arrangements of components may be used forcomputing device 300. The computing device 300 may be implemented in anymanner suitable for implementing the various functions described herein.

It will be appreciated that computer 300 depicted in FIG. 3 provides ageneral architecture and functionality suitable for implementingfunctional elements described herein and/or portions of functionalelements described herein. Functions depicted and described herein maybe implemented in software and/or hardware, e.g., using a generalpurpose computer, one or more application specific integrated circuits(ASIC), and/or any other hardware equivalents.

It is contemplated that some of the steps discussed herein as softwaremethods may be implemented within hardware, for example, as circuitrythat cooperates with the processor to perform various method steps.Portions of the functions/elements described herein may be implementedas a computer program product wherein computer instructions, whenprocessed by a computer, adapt the operation of the computer such thatthe methods and/or techniques described herein are invoked or otherwiseprovided. Instructions for invoking the inventive methods may be storedin fixed or removable media, transmitted via a data stream in abroadcast or other signal bearing medium, transmitted via tangible mediaand/or stored within a memory within a computing device operatingaccording to the instructions.

FIG. 4 depicts a flow diagram of a method according to one embodiment.Specifically, the method 400 of FIG. 4 is suitable for processing a datastream D for transmission, such as described above with respect to FIG.1.

At step 410, the data stream including data from one or more customersis received, such as by the virtual spectrum aggregated transmitter 110.

At step 420, the received data stream is sliced into N sub-streams,where each sub-streams is associated with a respective spectralfragment. Referring to box 425, the slicing of data streams intosub-streams may be performed using any of the following criteria, aloneor in any combination: per customer, per fragment, for data type, fixedsize, variable size, combination of various slicing methods and/or othercriteria.

At step 430, each of the sub-streams is modulated using a respectivemodulator. Referring to box 435, demodulators may be optimized for datatype, optimized for channel conditions, they share commoncharacteristics, they have various/different characteristics and so on.

At optional step 440, where one or more modulated sub-streams are to betransmitted using the same transponder or transmission channel, thesemodulated sub-streams are combined.

At step 450, the modulated sub-streams are up converted and transmitted.Referring to box 455, the up conversion/transmission process may bewithin the context of a satellite communication system, microwavecommunication system, wireless communication system/channel or othermedium.

FIG. 5 depicts a flow diagram of a method according to one embodiment.Specifically, the method 500 of FIG. 5 is suitable for processing one ormore received sub-streams, such as described above with respect to FIG.1.

At step 510, one or more modulated sub-streams are received and downconverted. Referring to box 515, one or more modulated sub-streams maybe received via a satellite communication system, wireless communicationsystem, wireless communication system/channel or other medium.

At step 520, any sub-streams previously combined at the transmitter areseparated to provide individual sub-streams, and at step 530 each of theindividual sub-streams is demodulated using a respective appropriatedemodulator.

At step 540, one or more of the demodulated sub-streams are selectivelydelayed so that the resulting demodulated data streams may be temporallyaligned.

At step 550, the demodulated and selectively delayed sub-streams arecombined to provide a resulting data stream such as a data stream D′representative of an input data stream D initially processed by thevirtual spectrum aggregator transmitter.

FIG. 6 depicts a flow diagram of a method according to one embodiment.Specifically, the method 600 of FIG. 6 is suitable for configuringvarious transmitter and receiver parameters in accordance with thevarious embodiments.

At step 610, a request is received for the transmission of customerdata. Referring to box 615, the request may provide a specifiedbandwidth, a specified data rate, a specified data type, specifiedmodulation type and/or other information describing the bandwidth and/orservice requirements associated with the customer data transmissionrequest.

At step 620, a determination is made as to the spectrum allocationsuitable for satisfying the customer data transmission request.

At step 630, an optional determination is made as to whether anyspecific spectrum related criteria is suitable for satisfying thecustomer data transmission request. Referring to box 635, such spectrumrelated criteria may include a minimum bandwidth block size, arequirement for contiguous bandwidth blocks and/or other criteria.

At step 640, available spectrum fragments are identified. Referring tobox 645, the identification of available spectrum fragments may be madewith respect to an allocation table, a management system and/or othersource of such information. In one embodiment, an allocation tabledefines the spectral allocation associated with each customer served bya satellite communications system; namely, the bandwidth allocation ofeach customer, the transponder(s) supporting the bandwidth, thesatellite(s) supporting the transponder(s) and so on. Additionally,available spectrum fragments are defined in terms of size and spectralregion for each transponder of each satellite.

At step 650, available spectrum fragments are allocated to satisfy thecustomer data transmission request. Referring to box 655, the availablespectrum fragments may be allocated as available, optimized for thecustomer, optimized for the carrier, optimized to reduce spectrumfragment count, optimized to provide resiliency or redundancy, and/oroptimized based on other criteria.

At step 660, transmitter/receiver systems are configured to provide thecorrect number and type of modulators/demodulators to support thecustomer data transmission request and adapt to any changes to spectrumfragment allocations for the requesting customer and/or other customers.That is, based upon optimization and/or other criteria, it may beappropriate to modify the spectral fragment allocations of multiplecustomers to optimize in favor of a particular customer, serviceprovider and the like.

At step 670, billing data, service agreements and the like are updatedas appropriate. At step 680, system configuration, provisioning and/orother management data is updated.

In various embodiments, spectral fragment available on differentsatellite transponders and/or different satellites are aggregated toform a virtual contiguous block. In other embodiments, the entirebandwidth of multiple transponders is used to support high data-ratepipes (e.g., OC-3/12c) over satellite links.

FIGS. 7-9 depict block diagrams of communication systems according tovarious embodiments. Each of the various components within thecommunication systems depicted in FIGS. 7-9 operates in substantiallythe same manner as described above with respect to correspondingcomponents within the communication system of FIG. 1. For example, ineach of the embodiments of FIGS. 7-9, an input data stream D is receivedby a virtual spectrum aggregated transmitter 110, where it is processedby a slicer/de-multiplexer x11 to provide N sub-streams (D₀ . . .D_(N-1)), where each of the N sub-streams is modulated by respectivemodulator x12. Other differences and similarities between the variousfigures will now be described more detail.

FIG. 7 depicts a single transponder embodiment in which a singletransponder is used to transport each of a plurality of data streamsdenoted as streams A, B, C and D. FIG. 7A depicts an uplink portion ofthe system, while FIG. 7B depicts a downlink portion of the system.

Referring to FIG. 7A, data streams A, B and C are modulated byrespective modulators 712 to produce respective modulated streams whichare then combined by a first signal combiner 113 ₁ to provide a combinedmodulated signal ABC.

Data stream D is processed by a slicer/de-multiplexer 711 to provide Nsub-streams (D₀ . . . D_(N-1)) which are then modulated by respectivemodulators 712 (i.e., modulators 712 ₀, 712 ₁ and 712 ₂) to providecorresponding modulated signals to be carried by respective spectralfragments S₀, S₁ and S₂. The corresponding modulated signals arecombined by a second signal combiner 713 ₂ to provide a combinedmodulated signal DDD, which is combined with modulated signal ABC by athird signal combiner 713 ₃. The resulting combined modulated signalsare converted by an up converter 714 to produce a carrier signal C whichis amplified by a power amplifier 720 and transmitted towards asatellite 740 via a satellite uplink 730.

Referring to FIG. 7B, satellite 740 transmits a modulated carrier signalincluding the modulated streams A through D to satellite downlink 750,which propagates the signal to a down-converter, 765. The down-convertedsignal is processed by a frequency de-multiplexer 164 ₃ which operatesto separate the signal into the ABC and DDD signal components.

The ABC signal components are separated by a second frequencyde-multiplexer 764 ₁ to recover the modulated signals and thendemodulated by respective demodulators 752.

The DDD signal components are separated by a third frequencyde-multiplexer 764 ₂ to recover the modulated signals which aredemodulated by respective demodulators 752.

The demodulated sub-streams D₀′, D₁′ and D₂′ are processed by a combiner761 to produce an output data stream D′ representative of the input datastream D. It is noted that each of the demodulators 162 operates in amanner compatible with its corresponding modulator 112.

FIG. 8 depicts a dual transponder embodiment in which a firsttransponder is used to transport each of a plurality of data streamsdenoted as streams A, B, and C, as well as two of three sub-streamsassociated with a data stream D, while a second transponder is used totransport each of a plurality of data stream denoted as E and F, as wellas the third sub-stream associated with the data stream D. FIG. 8Adepicts an uplink portion of the system, while FIG. 8B depicts adownlink portion of the system.

Referring to FIG. 8A, data streams A, B, C, E and F are modulated byrespective modulators 812 to produce respective modulated streams.

Data streams E and F are modulated by respective modulators 812 toproduce respective modulated signals.

Data stream D is processed by a slicer/de-multiplexer 711 to provide Nsub-streams (D₀ . . . D_(N-1)) which are then modulated by respectivemodulators 712 (i.e., modulators 712 ₀, 712 ₁ and 712 ₂) to providecorresponding modulated signals to be carried by respective spectralfragments S₀, S₁ and S₂.

The modulated signals associated with data streams A, B and C arecombined by a first signal combiner 813 ₁ to provide a combinedmodulated signal ABC.

The modulated signals associated with sub-streams D₀ and D₁ are combinedby a second signal combiner 813 ₂ to provide a combined modulated signalD₁₂.

The combined modulated signals produced by the first 813 ₁ and second813 ₂ signal combiners are then combined by a third signal combiner 813₃ and converted by a first upconverter 814 ₁ to produce a first carriersignal C1.

The modulated signals associated with sub-stream D₃ and streams E and Fare combined by a fourth signal combiner 813 ₃ and converted by a secondupconverter 814 ₂ to produce a second carrier signal C2.

The C1 and C2 carrier signals are combined by a fourth signal combiner,813 ₄, amplified by a power amplifier, 820, and transmitted towards asatellite, 840, via respective transponders (A and B) of a satelliteuplink 830.

Referring to FIG. 8B, satellite 840 transmits the two modulated carriersignals including the modulated streams A through F via respectivetransponders (A and B) to satellite downlink 850, which propagates thesignal to a down-converter 865. The down-converted signal is separatedinto its two carrier signals by frequency demultiplexer 864 ₄. The twocarrier signals are processed using various demultiplexers in 864,demodulators in 862 and combiner 861 to produce the various output datastreams A′ through F′ representative of the input data stream A throughF.

FIG. 9 depicts a dual satellite embodiment in which one satellite (940₁) is used to transport a plurality of data streams denoted as streamsA, B, and C, as well as two of the three sub-streams associated withdata stream D.A second satellite (940 ₂) is used to transport aplurality of data streams denoted E and F as well as the thirdsub-stream associated with data-stream D. FIG. 9A depicts an uplinkportion of the system while FIG. 9B depicts a downlink portion of thesystem.

Referring to FIG. 9A, data streams A, B, C, E and F are processed insubstantially the same manner as described above with respect to FIG.8A, except that the two carrier signals are not combined for transportvia respective transponders of a single satellite. Rather, FIG. 9 showstwo carrier signals amplified by separate power amplifiers (920 ₁ and920 ₂) and transmitted to satellites 940 ₁ and 940 ₂, respectively,using uplinks 930 ₁ and 930 ₂.

Referring to FIG. 9B, the two satellites 940 transmit their respectivemodulated carrier signals including modulated streams A through F viarespective downlinks 950, which are then fed to respectivedown-converters 965. The two down-converted carrier signals areprocessed using de-multiplexers (964), demodulators (962) and a combiner(961) to produce the output data streams A′ through F′ representative ofthe input data streams A through F.

FIG. 10 depicts a high-level block diagram of a slicer/de-multiplexersuitable for use in the various embodiments described herein.Specifically, the slicer/de-multiplexer 1000 of FIG. 10 comprises apacket encapsulator 1010, a master scheduler 1020 including a buffermemory 1022, and a plurality of slave schedulers 1030 including buffermemories 1032.

The packet encapsulator 1010 operates to encapsulate packets receivedfrom data-stream D into a packet structure having a predefined ornormalized format. While various encapsulating packet formats may beused, it is important that the combiner at a downlink side of a systembe configured to combine packets according to the encapsulating formatused by the slicer/de-multiplexer at an uplink side of the system.

In one embodiment, encapsulating packets comprise 188 byte packetshaving a 185-byte payload section and a three-byte header section. Thepacket encapsulator 1010 extracts a sequence of 185 byte portions fromthe original data stream D, and encapsulates each extracted portion toform encapsulating packet (EP). The header portion of each encapsulatingpacket stores a user sequence number associated with payload data suchthat the sequence of 185 byte portions of the data stream may bereconstructed by a combiner, such as described above with respect to thevarious figures.

In one embodiment, the user sequence number comprises a 14-bit numberthat is continually incremented and used to stamp encapsulated packetsprovided by the packet encapsulator 1010. In one embodiment, the headerportion of the packet provided by the packet encapsulator 1010 comprisesa first byte storing 47 hexadecimal (i.e. 47h), followed by 2 zero bits,followed by 14 bits associated with the user sequence number.

A larger sequence number field (e.g., 24 or 32 bits) may be used whenthe aggregate data rate being transported is higher. The size of thesequence number field is related to the amount of buffering that takesplace at the receiving combiner element described in various figuresabove. The size of the buffer, in turn, is related to the ratio of thelargest sub-stream bandwidth to the smallest sub-stream bandwidth. Thus,various embodiments may adjust the sequence number field size (and theresulting overhead) based on total aggregate bandwidth and/or the ratioof the highest to smallest bandwidth sub-streams.

In various embodiments, more or fewer than 188 bytes are used toconstruct encapsulating packets. In various embodiments, more or fewerthan three bytes are used to construct encapsulating packet headers. Forexample, by allocating additional header bits to the user sequencenumber a larger user sequence number may be used. In this case, thelikelihood of processing at a receiver two encapsulating packets havingthe same sequence is reduced.

In the embodiments described herein, the fixed packet size of 188 bytesis used for the encapsulating packets. However, in various alternateembodiments different fixed-sized packets and/or different variablesized packets may be used for different sub-streams as long as suchpacket sizes are compatible with the input interfaces of the respectivemodulators used for those sub-streams.

The master scheduler 1020 routes encapsulated packets to the variousslave schedulers 1030. The slave schedulers 1030 in turn route theirpackets to respective output ports of the slicer/demultiplexer, therebyproviding respective sub-streams to, illustratively, modulators or othercomponents.

Generally speaking, each slave scheduler 1030 accepts packets conformingto the bandwidth of the spectral fragment assigned to that scheduler.Thus, the slave scheduler servicing a 1 MHz spectral fragment channelaccepts packets at a data rate approximately 1/10 that of a slavescheduler serving a 10 MHz spectral fragment or region.

The master scheduler 1020 communicates with the slave schedulers 1030 toidentify which slave scheduler 1030 is (or should be) capable ofreceiving the next encapsulated packet. Optionally, the master scheduler1020 receives status and other management information from the slaveschedulers 1030, and some of this status information may be propagatedto various management entities (not shown).

In one embodiment, the slave schedulers 1030 provide a control signal tothe master scheduler 1020 indicative of an ability to accept the packet.In one embodiment, the master scheduler 1020 allocates packets to theslave schedulers 1030 in a round robin fashion. In one embodiment, wherecertain transmission channels or spectral regions are preferred basedupon customer and/or service provider requirements, the allocation ofencapsulated packet by the master scheduler 1020 is weighted in favor ofproviding more encapsulated packets to those slave schedulers 1030servicing the preferred transmission channels.

In one embodiment, each of the slave schedulers is associated with apredefined bandwidth or other indicators of channel capacity associatedwith the corresponding spectral fragment. In this embodiment, the masterscheduler 1020 routes packets according to a weighting assignment foreach slave scheduler 1030.

Generally speaking, the master scheduler routes packets according to oneor more of a random routing algorithm, a round robin routing algorithm,a customer preference algorithm and a service provider preferencealgorithm. Such routing may be accommodated by associating a weightingfactor with each modulator, spectral fragment, communications channel(e.g., transponder, microwave links, wireless channel etc.) and so on.For example, a preferred spectral fragment may comprise a fragmenthaving a minimum or maximum size, a fragment associated with arelatively low error or relatively high error channel, a fragmentassociated with a preferred communications type (e.g., satellite,microwave link, wireless network and so on), a fragment associated witha preferred customer and the like. Other means of weighting channels,communication systems, spectral regions and so on may also be usedwithin the context of the various embodiments.

FIG. 11 depicts a flow diagram of a method according to one embodiment.At step 1110, packets are received from data stream D. At step 1120,received packets are encapsulated. Referring to box 1125, the packet maycomprise 185 byte payload and three byte header packets. Other headerformats with a different sequence number field size and/or additionalcontrol information may be used within the context of the presentembodiments.

At step 1130 the encapsulated packets are buffered by, illustratively,the master scheduler 1020, a separate buffer (not shown) within thepacket encapsulator 1010 and so on.

At step 1140, encapsulator packets are forwarded (or caused to beforwarded) to the slave schedulers 1030 by the master scheduler 1020.

In the various embodiments described herein, each encapsulated packet iscoupled to a respective modulator as part of a respective sub-stream.However, in embodiments adapted to provide increased data resiliencyand/or backup, encapsulated packets may be coupled to multiplemodulators as part of multiple respective sub-streams. In theseembodiments, the sequence number associated with the encapsulated packetremains the same.

In these embodiments, a receiver will process the first encapsulatedpacket (or error-free encapsulated packet) having the appropriatesequence number and ignore other packets having the same sequencenumber. That is, when re-ordering encapsulating packets at the receiver,those encapsulating packets having a sequence number matching a sequencenumber of a recently ordered encapsulating packet are discarded. Sincesequence numbers are cyclical or repeated (e.g., every 16,384encapsulating packets in the case of a 14-bit sequence number), anencapsulating packet having the same sequence number of encapsulatingpacket processed several thousand packets ago is likely a duplicate ofthat previously processed encapsulating packet and, therefore, should bedropped or discarded as being redundant.

Various embodiments described herein provide dynamic spectrumaggregation of disjoint blocks of spectrum such that spectrum may beadded to or subtracted from existing spectrum allocations as customerbandwidth requirements change. Additionally, small or orphaned spectrumblocks (i.e., those spectrum blocks too small to generally be useful)may be virtually combined to form larger blocks of bandwidth.

The above-described embodiments provide a number of advantages,including improved system resiliency since the loss of any one spectralfragment will likely not cause a complete loss of service. In addition,when spectral fragments are mapped across multiple transponders, theloss of any one transponder does not result in a complete loss ofservice; rather, a graceful degradation of service is provided.Older/existing schemes utilizing contiguous spectrum are capable ofusing only one transponder which becomes a potential single point offailure.

Interference Mitigation and Improved Resiliency

For purposes of the following discussion, assume that a transmissionmechanism utilizes four carriers, S0 . . . S3 (though different numbersof carriers may be used). Further, that the carriers are separated (notadjacent) in the frequency domain such that any signal interferencepotentially affects only a subset (and not all) of the slices. Finally,assume that a control channel available (either in-band or out-of-band)for the receiver to provide feedback about the status of the signals tothe transmitter. These assumptions may be also by imputed to variousother embodiments discussed herein with respect to the various figures.

When a slice, Si, (0<=i<=3) is affected by interference, the receivingsite notices a degradation in the C/N (Carrier to Noise) of that slice.It informs the transmit side about the degradation using a controlchannel. The transmitter then decreases the FEC rate (makes the FECstronger, by changing to rate ⅔ from ¾, for e.g.) to enable the receiverthe combat the added noise. This scheme is called Adaptive Coding andModulation (ACM).

Various embodiments discussed herein may be used to enhance theeffectiveness of ACM by providing a capability to change the FEC rate ofonly a specific slice or portion of a data stream (rather than thetraditional approach of changing the FEC rate of the entire carrier ordata stream). In this manner, higher through put is maintained in thevarious embodiments vs. traditional techniques.

Various embodiments discussed herein provide that if an interferer istoo strong for any available FEC rate to mitigate its effects, then thereceiver loses lock on that carrier (e.g., carrier S2) and informstransmitter about the loss. The transmitter re-routes data over carriersS1, S3 and S4. In effect, it is “bypassing” spectral slice S2 andmaintains service albeit at a lower throughput. Contrast this withtraditional single-carrier schemes where a strong interferer would havecompletely impaired that carrier causing a complete loss of service.

Various embodiments discussed herein provide different carrierarrangements than previously known. Specifically, rather than thetraditional OFDM systems where a signal is comprised of a large numberof subcarriers that are adjacent to each other, the various embodimentsprovide separated and spectrally disjoint carriers. In this manner,front end saturation or pass-band impact of a strong interferer isgreatly attenuated in the various slices.

Various embodiments discussed herein enable slices to be transplanted orrerouted to different parts of the spectrum to combat interference,resulting in a complete restoration of service with little degradationin throughput.

Various embodiments discussed herein enable hitless delivery in thepresence of strong interference. For example, some embodiments configurea subset of carriers, such as S0 and S1, as a protection group such thatimpairment of either S0 or S1, but not both simultaneously, results inno loss of data. Under that scenario S2 and S3 may continue to operateas independent carriers without being members of any protection groups.Alternately, they may be grouped into a second protection group toprotect each other. As a third alternative, more than two carriers, sayS0 . . . S2, may form a protection group and S3 stays independent. Takento its extreme, all four carriers may be part of a protection group forcombating widespread interference, and so on. The degree of flexibilityis enormous and configurations can be fine-tuned to most effectivelydeal with the particular type of interference.

Various embodiments discussed herein enable the addition and deletion ofcarriers dynamically to further improve resiliency such as caused byequipment failures and/or interference. For example, a system may employtwo carriers, S0 and S1, acting independently (i.e., not constituting aprotection group) while a third carrier, S2, may be added later in aregion of available spectrum if either S0 or S1 are impaired. In oneembodiment, the third or spare carrier (e.g., S2) may be configured as asubstitute carrier, part of a temporary protection group, part of adynamically formed protection group.

As a substitute carrier, the spare carrier (e.g., S2) may be configuredto act as a “substitute” carrier for either S0 or S1 thus effectivelytaking over the purpose of the impaired carrier.

As part of a temporary protection group, the spare carrier (e.g., S2)may be configured to form a temporary protection group in alliance orassociation with the impaired carrier. For example, if S1 is impairedthen a protection group between S1 and S2 may be formed. S0 staysindependent. When the cause of the impairment is addressed restoring S1,then S2 may be removed.

As part of a dynamically formed protection group, the spare carrier(e.g., S2) may be configured as part of a dynamic formation ofProtection Groups among existing carriers, which is effective forcombating transient interference that affects multiple carriers fordurations long enough to cause packet loss and other impairments, but isnot long enough to mandate a complete re-routing of traffic as describedabove. For example, assume that S0 . . . S3 constitute a four-carriertransmission system, and S2 and S3 experience transient interferencethat neither per-carrier ACM nor re-routing can effectively address. Inthis embodiment, S2 and S3 are temporarily paired to constitute a DSSProtection Group while S0 and S1 stay independent. The net result is arobust way of dealing with interference with a temporary reduction inthroughput. Once the root cause of the impairments affecting S2 and S3are addressed, they can be reconfigured to act independently.

Disjoint Replicated Spread Spectrum (DRSS)

The various techniques and embodiments described herein may be adaptedto provide Disjoint Replicated Spread Spectrum (DRSS) embodiments whichprovide “hitless” delivery of payload data in the presence of strongRadio Frequency (RF) interference in wireless communication channels.For example, traditional techniques for wireless communications involvesuse of single-carrier RF signals that have error-protection code ratesdesigned to deliver Quasi Error Free (QEF) data given theCarrier-to-Noise (C/N) ratio of the communications channel. In thepresence of increased interference, the error-protection code rate isreduced (made stronger) to help negate the effects of degradation of thesignal at the receiver. A problem with this approach is that asufficiently strong interferer that is in-band with the received signaland which results in a C/N ratio being lower than the QEF threshold canresult in complete loss of data, no matter how strong the code rate.This may be due to (among other reasons) complete saturation of thereceiver's front-end RF down-conversion circuitry involving componentssuch as LNAs, mixers and sampling circuits using Analog-to-DigitalConverters (ADC). Thus, even the best error-coding technique based onsingle-carrier systems cannot combat interference that is in-band andgreater than the carrier power by the QEF C/N threshold.

DRSS utilizes multiple spectrally-disjoint carriers. In the DRSStechnique, the original payload (P) is transmitted over N (N>=2)carriers, each coded and modulated, in the general case, with differentphysical layer schemes suitable for their respective channel conditions.In a simple embodiment, all carriers are constructed using the samephysical-layer parameters but transmitted in spectral blocks that aredisjoint (separated) from each other. Carriers, in general, do not haveto be of the same spectral bandwidth. However, the information carryingcapacity (as determined by the symbol rate, code rate, constellationmap, roll-off and other relevant modulation parameters) of each carrieris required to be sufficient to carry the required payload.

At the transmit end, the payload (P) is first pre-processed and brokenup into a sequence of fixed-size packets (p_(i), i=0, 1, 2, . . . )using the virtual spectrum aggregation (VSA) techniques described above.Each packet p_(i) at the output of the VSA pre-processor is thenreplicated N times, and each copy is transmitted over all N carriers.

At the receive end, the receiver demodulates data from each carrier.When all carriers have good C/N, the receiver will recover N error-freecopies of each packet, p_(i). N−1 copies are discarded and one retainedfor packet p_(i) for each i. All selected copies are provided to the VSAprocessor at the receive end where the original payload, P, isreconstructed and delivered to its intended recipient again as describedabove.

In the presence of strong interference, a subset of the N carriers mayexperience complete loss of data. However, as long as at least onecarrier has its C/N above its QEF threshold at any given time, thereceiver will have access to at least one good copy (out of the N copiestransmitted) of each packet, p_(i). This enables the VSA processor atthe receiver to reconstruct the payload error-free.

In the above scheme, multiple spectrally-disjoint carriers are lesslikely to be simultaneously affected by the same interfering signalunless it happens to be extremely broadband. Strong interference mayresult in a complete loss of data in up to N−1 carriers, but completerecovery of the desired payload is still possible as long as for eachpacket, p_(i), there's at least one carrier that is able to deliver thatpacket error-free. For interference that moves rapidly in the spectraldomain, this may imply that consecutive packets are derived fromdifferent carriers due to the possibility that a carrier that deliveredpacket p_(i), may experience interference thereafter and may not be themost suitable carrier for delivering packet p_(i+1).

Use of the VSA techniques described with respect to FIGS. 1-11 and theirassociated description allow aggregation of multiple, disjoint spectralslices. When DRSS is used in conjunction with spectral aggregation, apowerful new capability is enabled. For instance, selective use of DRSSenables mapping of carriers to portions of spectrum (such as unlicensedbands) that may be prone to interference. In other words, use of DRSSenables a service provider to start to use noisy or unlicensed bands bymapping either the entire set or a subset of the carriers beingaggregated to potentially noisy bands while still delivering theconstituent payloads with a high degree of resiliency.

FIG. 12 depicts a high level block diagram of a system benefiting fromvarious embodiments. Specifically, FIG. 12 depicts a high level blockdiagram of a system 1200 that uses the above-described VSA techniques toaggregate, illustratively, four spectral slices S1-S4 includingredundant payload communicated over spectral slices S2 and S3. Theexemplary system 1200 is a hybrid VSA/DRSS system that transports apayload P using carriers S0, S1, S2 and S3. The exemplary system 1200 isdepicted as utilizing a satellite communications link 1260, though otherand additional types of communications links may be employed.

The system 1200 generally contemplates a VSA preprocessor, amodulator/transmitter, a communications link, a demodulator/receiver anda VSA postprocessor.

The VSA preprocessor 1210 performs the various slicer functions 1212,parity codes functions 1214, control header insertion functions 1216 andscheduler functions 1218 as discussed herein. The VSA preprocessor 1210is adapted to process or slice an input signal or stream payload P into,illustratively, four stream portions or segments denoted as P′₀ throughP′₃. As previously noted, each of the four stream portions or segmentswill be modulated in a manner conforming to a respective spectral sliceof a carrier signal, such as a transmitted via a communications link.

The modulator/transmitter comprises, illustratively, four modulators1220-1 through 1220-4 adapted to respectively modulate payload streamportions or segments as P′₀ through P′₃ to produce modulated signalsS_(o) through S₃, which modulated signals are combined by singlecombiner/multiplexer 1230. The resulting combined signal is processed byupconverter 1240 and amplifier 1250 to provide, illustratively, a signalsuitable for transmission via a communications link 1260.

The communications link 1260 is depicted as a satellite communicationslink including a transmitter 1260-T which sends the transmission signalto a receiver 1260-R via a satellite 1260-S.

The demodulator/receiver comprises, illustratively, a signalseparator/demultiplexer 1270 which extracts the modulated signals S_(o)through S₃ from the received satellite signal, and four demodulators1280-1 through 1280-4 adapted to demodulate the modulated signals S_(o)through S₃ and retrieve therefrom payload stream portions or segmentsP′₀ through P′₃.

The VSA postprocessor 1290 performs various buffer manager functions1291, buffer functions 1292, no packet deletion functions 1293, paritycode processor functions 1294, re-sync and alignment functions 1295,control header removal functions 1296 and combiner functions 1297 asdiscussed herein. The VSA postprocessor 1290 is adapted to process theillustratively, four stream portions or segments denoted as P′₀ throughP′₃ to reassemble the input signal or stream payload P.

In various embodiments, Spectral Slices S0 and S1 that are independentcarriers do not use DRSS. These carrier are assumed to be mapped to“clean” spectrum where strong interference is not usually a problem andstandard code rates (such as LDPC ¾, ⅚ and the like, along with a blockcode such Reed Solomon or BCH) is sufficient for each carrier.

In various embodiments, Spectral Slices S2 and S3 use DRSS. In otherwords, the payload carried in S2 is replicated and sent over carrier S3.Both S2 and S3 use standard coding techniques (such as LDPC ¾ or ⅚, etc.along with a block code such as BCH or Reed Solomon). This exampleassumes that carriers S2 and S3 will be mapped to spectrum that may havestrong interferers (e.g., malicious or unintentional) capable of causingcomplete loss of data loss in either S2 or S3. By ensuring a spectralgap between S2 and S3, the probability of interference simultaneouslyaffecting S2 and S3 is minimized. Thus, the aggregated signal may berecovered so long as both S2 and S3 are not affected by interferenceabove a threshold.

In various embodiments, the system is configured such that aggregatecapacity of S0, S1 and S2 is sufficient to transport payload P. Asimilar assumption is made for the aggregate capacity of S0, S1 and S3.

The payload P is sliced into small fixed-size packets, and a controlheader is inserted at the beginning of each packet conformant to the VSAtechnique described above. Additional parity codes are appended to allowthe receiver to check for header integrity. Three separate schedulers,one each for S0 and S1, and one for the combined set of S2 and S3, areused for allocating the packets to three separate streams denoted P₀′,P₁′ and P₂₀′. P₂₁′ is a replica of P₂₀′. The schedulers ensure that theamount of data allocated to each carrier does not exceed itsinformation-bearing capacity.

In various embodiments, P₀′, P₁′, P₂₀′ and P₂₁′ are fed to separatemodulators (Mod0, Mod1, Mod2 and Mod3, respectively) to generatecarriers S0, S1, S2 and S3. In various other embodiments, compositemodulators are used.

The four carriers are combined using a standard RF combiner,up-converted to the desired frequency band, amplified using a PowerAmplifier (PA) and then radiated using an antenna. A bent-pipe satellitesends the signal to potentially multiple receiving sites.

On the receive side, the four carriers are demodulated by four separatedemodulators. Packets from the demodulators are queued in separatebuffers (one per demodulator). This is necessary because propagationdelays of the four carriers may be quite different and may vary overtime. Null packets (e.g., introduced by modulators if using DVB-S orDVB-S2 as the physical layer standard) are removed and parity codes arechecked to detect and correct control header information vital for thecorrect processing of the four packet streams. Packets with incorrectparity codes are dropped. A Resynchronization and Alignment blockensures that packets from all available streams are properly sequenced,and duplicate packets received over carriers S2 or S3 (e.g., as wouldhappen when both signals have a good C/N) are dropped. Control headersare stripped and the payload sections of the packets are merged togenerate the final payload P.

Interference in S2 and S3 may be localized to specific receive sites or,if present at the transmit side, would impact those signals at allreceive sites. In case of localized interference, certain sites mayexperience a partial or complete loss of data in, say, S2. In thosecases, the packets received over S3 are chosen. At other receiver sites,S3 may be impaired in which case packets received over S2 are chosen. Ifthe interference is a sweeper type that may alternately affect S2 andS3, then receivers resort to switching between those two carriers on aper-packet basis.

The system 1200 is depicted as using a bent-pipe satellitecommunications link 1260. However, in various other embodiments, othertypes of wireless networks such as a point-to-multipoint terrestrialbroadcast system or a point-to-point microwave system for cellularbackhaul may be used. More generally, the system can be effectivelyapplied for transport of any data payload (whether synchronous orpacketized) over a wireless channel.

In still other embodiments, one or more of the modulated signals isconveyed via an alternate network 1265, such as an optical network, IPnetwork or other wireline network.

Various benefits of the embodiments include significantly higherspectral usage efficiency as well as the ability to use orphanedspectral fragments that are too small to use otherwise. The variousembodiments are applicable to satellite applications, point-to-pointwireless links such as those used in bent-pipe SatCom applications,wireless backhaul infrastructure such as provided using microwave towersand so on.

The various embodiments provide a mechanism wherein bandwidth may beallocated by “appending” additional blocks of bandwidth to thosebandwidth blocks already in use, thereby facilitating a“pay-as-you-grow” business model for service providers and consumers.

In various embodiments, a single transponder in a satellite system isused to propagate a carrier signal including a plurality of modulatedsub-streams, each of the modulated sub-streams occupying its respectivespectral fragment region. In other embodiments, multiple carrier signalsare propagated via respective transponders.

In various embodiments, a single microwave link within a microwavecommunication system is used to propagate a carrier signal including aplurality of modulated sub-streams, each modulated sub-stream occupyingits respective spectral fragment region. In other embodiments, multiplecarrier signals are propagated via respective microwave links.

In various embodiments, a single wireless channel within a wirelesscommunication system is used to propagate a carrier signal including aplurality of modulated sub-streams, each modulated sub-stream occupyingits respective spectral fragment region. In other embodiments, multiplecarrier signals are propagated via respective wireless channels.

Efficient Failover Support Using Protection Groups

By segmenting a stream into a plurality of stream segments andtransmitting these stream segments via respective spectral portions,resiliency to interferers such as from malicious sweepers, leakyequipment and the like may be improved.

Various embodiments further improve resiliency by replicating streamsegments and modulating/transmitting the replicated stream segments viaa different spectral region, optionally using a different modulationtechnique. In some embodiments, an original or replicated stream segmentmay be conveyed by a wireline communications link, as discussed above.

Various embodiments further improve resiliency by providingsegment-level protection groups in which a stream segmentmodulated/transmitted within a first spectral region ismodulated/transmitted within a backup spectral region in response tochannel impairments within the first spectral region exceeding athreshold level. In various embodiments, the backup spectral regioncomprises a spectral region associated with a lower priority data streamsegment. In various embodiments, priority is assigned according to typeof data, customer, service level agreement (SLA) profile and/or othercriteria.

In various embodiments, rather than allocating a block of activespectrum and another equally large block of backup spectrum that remainsunused, several smaller blocks of spectrum are utilized. The spectrumblocks may be allocated to the same or different satellites (or otherwireless communications mechanisms), the same or different transpondersand so on. For exemplary purposes, it is assumed that the bandwidthcapacity of each of the smaller spectral blocks is the same, though thisis not a requirement of the various embodiments. Within the context of abackup spectral block or region, the backup spectral block or regionshould be at least as large as the largest spectral block or region.Where the spectral blocks or regions are of similar size, the backupspectral block or region will also be of the similar size.

In various embodiments, information such as channel status feedback isreceived at the transmitter. Referring to FIG. 12, optional statusfeedback (SF) may be received via the alternate network 1265 or anyother mechanism. For example, in the typical satellite system a backchannel exists which may be used by the receiver to convey informationto the transmitter indicative of transmission quality, error rate,buffer back pressure, receiver status and so on. In the variousembodiments discussed herein, any of the known mechanisms for providingfeedback or status information from a receiver to transmitter may beemployed.

FIG. 13 depicts a flow diagram according to one embodiment.Specifically, FIG. 13 depicts a flow diagram of a mechanism forproviding enhanced channel resiliency with optional prioritizationaccording to the various embodiments. The methodology discussed hereinwith respect to FIG. 13 may be provided at one or more VSA transmitterssuch as discussed above.

At step 1310, one or more data streams are received from one or morecustomers. Referring to box 1315, the one or more data streams may bereceived via satellite link, microwave link, wireless channel, wirelinechannel and/or other means.

At step 1320, each of the data streams is sliced into a plurality ofstream segments and/or sub-streams, each of the stream segments and/orsub-streams being associated with a respective spectral fragment asdiscussed above with respect to the various embodiments. Referring tobox 1325, the stream segments and/or sub-streams may defined accordingto customer, available spectral fragments of fixed size or variablesize, data type, signal type and/or other parameters.

At step 1330, the various modulation parameters, bandwidth allocations,priority levels and/or other parameters are selected for the streamsegments and/or sub-streams and their respective spectral fragments. Thevarious stream segments and/or sub-streams are accordingly modulated andtransmitted within their respective spectral fragments.

At step 1340, the various channels associated with the spectralfragments are monitored to identify suboptimal channel behavior, such aschannel interference, channel impairments and the like. Referring to box1345, such monitoring may occur at predetermined intervals, after eachrelevant subscriber event, after a predetermined number of subscriberevents or according to some other schedule. For example, in variousembodiments interrupt-driven monitoring is provided wherein receiversonly convey information to respective transmitters when a channel isimpaired beyond one or more threshold levels, such as one or more levelscorrectable by adapting forward error correction (FEC) parameters, alevel beyond FEC correction ability, a level indicative of channelfailure and so on.

At step 1350, suboptimal channels are processed according to channelperformance and/or priority level of channel data. Referring to box1355, the forward error correction (FEC) and/or other parametersassociated with the channel may be adapted. Such adaptation may be basedupon various thresholds, such as one or more of interference thresholds,one or more impairment thresholds and so on. Within the context ofpriority level processing (such as where a channel is effectivelynonfunctioning), the stream segments and/or sub-streams associated withthe channel may be modulated and transmitted via a backup channel(s) orchannel(s) associated with lower priority data. That is, a scheduler mayadapt the various schedules to accommodate priority segments and/orsub-streams preferentially over lower priority segments and/orsub-streams.

At step 1360, segments and/or sub-streams are optionally aggregated overmultiple spectral fragments such that they are transported via multiplecommunications channels. Additionally, the multiple communicationschannels may be supported via different communications networks orlinks. Referring to box 1365, various links include one or more of apoint to point links such as satellite links or microwave links, pointto multipoint links such as provided by various wireless channels,wireline channels and/or other mechanisms.

The above-described steps contemplate, in response to channel qualitydegradation or failure, one or both of individual processing of channelsto adapt FEC and/or other parameters and channel reallocation based uponpriority of data. These steps are implemented in a substantiallyautomatic manner in response to service level agreement (SLA), profiledata, default carrier preferences and/or other criteria. Generallyspeaking, the systems operate in a substantially automated manner toensure that prioritized data channels are used as efficiently aspossible. Different data streams may be associated with differentpriority levels. Different customers may be associated with differentpriority levels.

Various embodiments operate to provide automatic rerouting of data by aVSA transmitter over available spectral blocks to bypass one or morefailed spectral blocks. Various embodiments operate to provide automaticrerouting of data by the VSA transmitter to provide load balancingfunctions or otherwise utilize available spectral blocks as efficientlyas possible.

As previously discussed, various prioritization techniques may beemployed to ensure that high-priority traffic is guaranteed delivery,while low-priority traffic is delivered using spare bandwidth left overfrom servicing the higher priority traffic or opportunistically inserteddata.

Various embodiments support multiple prioritization levels such as byusing a Weighted Fair Queuing (WFQ) scheduler for allocation to thevarious traffic classes.

Various embodiments provide interference mitigation using spectralaggregation. That is, when an interferer (whether CW or complex innature) degrades a particular channel, only the FEC rate of thatparticular channel is adapted to compensate for this degradation. If theinterferer is too strong to be overcome with better FEC code rates alone(or so strong that the adapted FEC code rate may drop the throughput tounacceptably low levels), then the channel must be reallocated to adifferent spectral fragment. In particular, the various embodimentsprovide interference mitigation per-slice FEC rate adjustment (FEC rateof each slice is adjusted depending upon the degree of interferencespecific to each slice) and spectral slice reallocation (IF interferencewithin a specific slice is too strong and cannot be mitigated with ahigher FEC rate, that slice rather than the entire set of slices isrelocated to another region of the transponder or another transponderentirely without affecting the other slices).

Various embodiments are adapted to provide improved security viaencryption of some or all of the data segments associated with a datastream. That is, in various embodiments channel modulation circuitry isadapted to include encryption functionality, while channel demodulationcircuitry is adapted to include decryption functionality. Suchencryption/decryption functionality may be based on the use of largeencryption keys, frequently changed encryption keys or some combinationthereof. Techniques such as AES may also be utilized within the contextof the various embodiments. The use of the VSA techniques describedherein provide additional layers of security even without encryption.With encryption security becomes extremely robust.

In one embodiment, each data segment and/or channel is encrypted with acommon encryption key or technique. In other embodiments, each datasegment and/or channel is encrypted with a respective encryption key ortechnique.

Various embodiments contemplate a system, method, apparatus, computingdevice and the like operable to perform the various steps and functionsdiscussed herein, such as dividing a data stream into a plurality ofsub-streams; modulating each sub-stream to provide a respectivemodulated signal adapted for transmission via a respective spectralfragment or block; monitoring data indicative of channel performance foreach of the spectral fragments to identify degraded channels; andadapting, for each degraded channel, one or more respective modulationparameters to compensate for respective identified channel degradation.

In various embodiments, the one or more modulation parameters areadapted to compensate for identified channel degradation up to athreshold level of degradation. FEC rate and/or other parameters may beadjusted to accomplish this. A spectral gap may be maintained betweenvarious spectral fragments or blocks.

In the case of the degradation of an identified channel exceeding athreshold level (e.g., too many errors to correct, too many errors tocorrect and have sufficient bandwidth etc.) or the channel simplyfailing, then various embodiments operate to select a backup spectralfragment for use by the modulated signal associated with the identifieddegraded channel. The sub-stream may need to be remodulated or modulatedin a different manner for the newly selected spectral fragment or block.Prioritization among data stream and/or sub-streams may be provided inthe case of a limited number of spectral fragments or blocks.

Various embodiments contemplate compound or multiple sub-streams withinat least some of the spectral fragments or blocks, such as by combiningtwo or more modulated sub-streams to form respective combinedsub-streams, each of the combined sub-streams being modulated onto amodulated signal adapted for transmission via a spectral fragment havinga bandwidth compatible with the total effective data rate of combinedsub-streams.

Various embodiments contemplate transmitting carrier signals viarespective channels within a communications system. For example, each ofone or more carrier signals may be supported by a respective transponderwithin a satellite communications system, a respective microwave linkwithin a microwave communications system, and/or a respective wirelesschannel within a wireless communications system.

Various embodiments contemplate dividing a data stream into a pluralityof sub-streams by encapsulating sequential portions of the data streaminto payload portions of respective encapsulating packets, each of thesequential portions of the data stream being associated with arespective sequence number included within a header portion of therespective encapsulating packet; and including each encapsulating packetwithin a respective sub-stream. Alternatively, each encapsulating packetmay be included within one or more of the sub-streams. The sequencenumber may be represented by a field having at least 14 bits. Theencapsulating packet header may includes a hexadecimal 47 in a firstbyte.

Various embodiments contemplate a receiver for receiving each of themodulated sub-streams via respective spectral fragments; demodulatingeach of the modulated sub-streams; and combining a plurality of thedemodulated sub-streams to recover the data stream. Combining thedemodulated sub-streams to recover the data stream may be provided viaordering encapsulating packets received via one or more sub-streamsaccording to their respective sequence numbers; and extractingsequential portions of the data stream from the ordered encapsulatingpackets to recover thereby the data stream. Discarding of encapsulatingpackets having a sequence number matching the sequence number of arecently received encapsulating packet may also be provided.

While the foregoing is directed to various embodiments of the presentinvention, other and further embodiments of the invention may be devisedwithout departing from the basic scope thereof and those skilled in theart can readily devise many other varied embodiments that stillincorporate these teachings. As such, the appropriate scope of theinvention is to be determined according to the claims, which follow.

1. A method comprising: dividing a data stream into a plurality ofsub-streams; modulating each sub-stream to provide a respectivemodulated signal adapted for transmission via a respective spectralfragment; monitoring data indicative of channel performance for each ofthe spectral fragments to identify degraded channels; and adapting, foreach degraded channel, one or more respective modulation parameters tocompensate for respective identified channel degradation.
 2. The methodof claim 2, wherein said one or more modulation parameters are adaptedto compensate for identified channel degradation up to a threshold levelof degradation.
 3. The method of claim 1, wherein said one or morechannel parameters include a forward error correction (FEC) rate.
 4. Themethod of claim 1, further comprising: in response to degradation of anidentified channel exceeding a threshold level, selecting a backupspectral fragment for use by the modulated signal associated with theidentified degraded channel.
 5. The method of claim 4, furthercomprising: modulating the sub-stream associated with the identifieddegraded channel to provide a respective modulated signal adapted fortransmission via the new spectral fragment.
 6. The method of claim 4,wherein the backup spectral fragment comprises a spectral fragmentsupporting a low priority sub-stream.
 7. The method of claim 4, whereinsaid new spectral fragment comprises a spectral fragment associated witha lower priority sub-stream.
 8. The method of claim 4, wherein saidthreshold level of degradation for a channel is defined by a bandwidthrequirement of the respective modulated sub-stream including an optimalFEC rate and a bandwidth capacity of the channel.
 9. A method,comprising: dividing a data stream into a plurality of sub-streams, eachof said sub-streams being modulated for transmission via a respectivespectral fragment; allocating one or more modulation parameters to eachof said sub-streams according to a data rate of the respective spectralfragment; monitoring signals indicative of performance for each of saidspectral fragments to determine respective threshold levels ofthroughput; and adapting a respective forward error correction (FEC)rate for each sub-stream supported by a spectral fragment experiencing areduced throughput.
 10. The method of claim 9, wherein the one or moremodulation parameters include a specific bandwidth parameter.
 11. Themethod of claim 9, wherein the spectral fragments associated withoptimal throughput characteristic maintain an optimal FEC rate.
 12. Themethod of claim 9, wherein each of the spectral fragments is associatedwith a portion of an upconverted carrier signal.
 13. The method of claim12, wherein at least some of the spectral fragments are additionallyassociated with a portion of at least a second upconverted carriersignal.
 14. The method of claim 13, wherein the first and second carriersignals are conveyed using different point to point links.
 15. Themethod of claim 13, wherein the first and second carrier signals areconveyed using different point to multipoint links.
 16. The method ofclaim 9, further comprising rerouting sub-streams from failed spectralfragments to backup spectral fragments.
 17. The method of claim 16,wherein said rerouting is performed in a prioritized manner.
 18. Themethod of claim 9, wherein modulating the sub-streams to providemodulated signals adapted for transmission via the respective spectralfragments comprises modulating at least one of the sub-streams into aplurality of modulated signals.
 19. The method of claim 18, whereinthere is a spectral gap between at least two of the plurality ofmodulated signals.
 20. The method of claim 9, further comprisingcombining two or more modulated sub-streams to form respective combinedsub-streams, each of said combined sub-streams being modulated onto amodulated signal adapted for transmission via a spectral fragment havinga bandwidth compatible with the total effective data rate of combinedsub-streams.
 21. The method of claim 9, further comprising transmittingsaid carrier signals via respective channels within a communicationssystem.
 22. The method of claim 9, wherein each of said one or morecarrier signals is supported by one of a respective transponder within asatellite communications system and a respective microwave link within amicrowave communications system.
 23. The method of claim 9, wherein eachof said one of more carrier signals is supported by a respectivewireless channel within a wireless communications system.
 24. The methodof claim 9, wherein said dividing a data stream into a plurality ofsub-streams comprises: encapsulating sequential portions of said datastream into payload portions of respective encapsulating packets, eachof said sequential portions of said data stream being associated with arespective sequence number included within a header portion of therespective encapsulating packet; and including each encapsulating packetwithin a respective sub-stream.
 25. The method of claim 9, wherein saiddividing a data stream into a plurality of sub-streams comprises:encapsulating sequential portions of said data stream into payloadportions of respective encapsulating packets, each of said sequentialportions of said data stream being associated with a respective sequencenumber included within a header portion of the respective encapsulatingpacket; and including each encapsulating packet within one or more ofsaid sub-streams.
 26. The method of claim 24, wherein said sequencenumber is represented by a field having at least 14 bits.
 27. The methodof claim 26, wherein said encapsulating packet header further includes ahexadecimal 47 in a first byte.
 28. The method of claim 9, furthercomprising: receiving each of the modulated sub-streams via respectivespectral fragments; demodulating each of the modulated sub-streams;combining a plurality of the demodulated sub-streams to recover the datastream.
 29. The method of claim 28, wherein combining the demodulatedsub-streams to recover the data stream comprises: ordering encapsulatingpackets received via one or more sub-streams according to theirrespective sequence numbers; and extracting sequential portions of saiddata stream from said ordered encapsulating packets to recover therebysaid data stream.
 30. The method of claim 29, further comprisingdiscarding encapsulating packets having a sequence number matching thesequence number of a recently received encapsulating packet.
 31. Acomputer readable medium including software instructions which, whenexecuted by a processer, perform a method comprising: dividing a datastream into a plurality of sub-streams, each of said sub-streams beingmodulated for transmission via a respective spectral fragment;allocating one or more modulation parameters to each of said sub-streamsaccording to a data rate of the respective spectral fragment; monitoringsignals indicative of performance for each of said spectral fragments todetermine respective threshold levels of throughput; and adapting arespective forward error correction (FEC) rate for each sub-streamsupported by a spectral fragment experiencing a reduced throughput. 32.A computer program product, wherein a computer is operative to processsoftware instructions which adapt the operation of the computer suchthat computer performs a method comprising: dividing a data stream intoa plurality of sub-streams, each of said sub-streams being modulated fortransmission via a respective spectral fragment; allocating one or moremodulation parameters to each of said sub-streams according to a datarate of the respective spectral fragment; monitoring signals indicativeof performance for each of said spectral fragments to determinerespective threshold levels of throughput; and adapting a respectiveforward error correction (FEC) rate for each sub-stream supported by aspectral fragment experiencing a reduced throughput.
 33. An apparatus,comprising: a splitter, for dividing a data stream into a plurality ofsub-streams, each of said sub-streams associated a respective spectralfragment and having a data rate compatible with a bandwidth of therespective spectral fragment; a plurality of modulators, each modulatorconfigured to modulate a respective sub-stream to provide a modulatedsignal adapted for transmission via the respective spectral fragment;and at least one upconverter, for upconverting said modulated signalsonto respective spectral fragments of at least one carrier signal;wherein the sub-streams included within the upconverted modulatedsignals are adapted to be demodulated and combined at a receiver torecover thereby data stream.
 34. The apparatus of claim 33, wherein saidsplitter comprises: an encapsulator, for encapsulating sequentialportions of said data stream into payload portions of respectiveencapsulating packets, each of said sequential portions of said datastream being associated with a respective sequence number includedwithin a header portion of the respective encapsulating packet; and amaster scheduler, for selectively routing encapsulated packets towardsthe demodulators.
 35. The apparatus of claim 33, wherein said splitterfurther comprises a plurality of sub schedulers, each of said subschedulers adapted to route packets received from the master schedulertoward a respective modulator.
 36. The apparatus of claim 34, whereinsaid master scheduler routes packets according to one of a randomrouting algorithm and a round robin routing algorithm.
 37. The apparatusof claim 33, wherein said master scheduler routes packets according toone of a customer preference algorithm and a service provider preferencealgorithm, wherein each sub-stream is associated with a respectiveweight.
 38. The apparatus of claim 36, wherein the respective weight ofa sub-stream is defined by one or more of a preferred spectral fragment,a preferred spectral fragment type, the preferred communication channel,a preferred communication channel type, a preferred traffic type and apreferred customer.